Polyamides stabilized with manganous silicate and process for producing same



United States Patent I 3,300,443 POLYAMIDES STABILIZED WITH MANGANOUS SILICATE AND PROCESS FOR PRODUCING SAME Luigi Ciceri, Como, and Pierluigi Perazzoni, Palazzolo Milanese, Italy, assignors to Snia Viscosa Societa Nazionale- Industria Applicazioni Viscosa S.p.A., Milan, Italy, a company of Italy No Drawing. Filed June 14, 1963, Ser. No. 287,767 Claims priority, application Italy, June 20, 1962,. 12,428/ 62 Claims. (Cl. 26045.75)

' It is known that polyamide yarns when exposed to light, are subjected to a substantial degradation which is more particularly marked when titanium dioxide is present in the yarn as dull finishing.

The sensitivity of the yarn in the presence of light increases with its content of titanium dioxide and when said content ranges between 0.4 and 3% by weight, the degradation is even rapid.

It has already been proposed to reduce the degrading catalytic effect of the titanium dioxide in the presence of light, by incorporating manganese compounds into the polymer.

However, the use of manganese compounds is somewhat difiicult insofar as at the temperature at which the polymerization iscarried out and in the presence of water such compounds generally become brown thus colouring the polymer.

Especially to prevent such a coloration of the yarns, it has been proposed to resort to manganese salts having a reducing anion, as described in the U.S. specification 4 Applying certain treating conditions, however, for instance bleaching the yarn by the oxidizing action of chlorite also the addition of said compounds leads to the coloration of the yarn.

Other prior propositions relate to compounds of manganese with phosphoric acids (see U.S. Patent 2,984,647), the nonsoluble pyrophosphates appearing as suitable for use'as concerns the avoidance of the coloration of the yarn. 'Their protective activity against the degradation of the polymers by light is however not very satisfactory and'especially is rather unstable.

Now, it has surprisingly been found that the introduction of the silicate of bivalent manganese into polyamide yarns results in a very good protective effect against the degradation by light, and that by adding it even in con- 'siderable amounts there does not result any change of colour after the influence of light or after the action of oxodizing agents.

The use of the silicate of bivalent manganese, owing to its substantially complex and large molecule, has not been taken into consideration hitherto. Moreover being completely insoluble it was assumed that the salt should enter into the polymer in a non-ionized and completely inactive form.

I The use of the silicate of bivalent manganese as compared with that of soluble manganese salts shows the advantage that there may be used substantial amounts without any modification of the viscosity of the polymer and without any coloration effect during an oxidizing treatment of theyarns.

Thus, for instance, it is possible to introduce into a polyamide such an amount of manganous silicate as to reach a 0.05 content by weight of the polymer-calculated as metallic manganese-whereby there is obtained a yarn which shows an extremely high light fastness. In comparison with the amount of other manganous com pounds for instance, as suggested by the above mentioned U.S. Patent 2,887,462 one may observe that those do ice not rise above 0.01% by weight of manganese in proportion to the polymer, and, in fact, if said contents are increased using the manganese compounds suggested hitherto, an unacceptable coloration of the polymer appears.

Experiments have shown that an outstanding light fastness is obtained using manganous silicate in such. amounts as to provide a percentagecalculated as manganese metalwhich varies between 0.01 and 0.05% by weight of the polymer, although even amounts as small as 0.005% have provided substantial results.

It is possible to use either naturally occurring manganous silicates previously purified by eliminating the impurities (carbonates or oxidized manganese salts) in a suitable mannerfor instance by washing them with acetic acidor synthetic manganous silicate obtained by fusing silica together with a manganous salt as. for instance manganous carbonate. Operating in this latter way a glass-like manganous material is obtained showing a yellow colour in the amorphous state assuming however a pale pink colour after its devitrification (i.e. in the crystalline state) and having a manganese content which may vary from 15 to 43% of its total weight.

To obtain good results with such a compound it is absolutely necessary to crush it into extremely fine particles so as to obtain a powder which examined for instance with the aid of a sedimentation test shows no more the 10% of particles with a size greater than 5 microns but practically no particle reaching a size of 10 microns.

The invention is characterized by the fact that the artificial or natural manganous silicate in afinely crushed and purified state, is incorporated either into the polyamides forming monomersor into the solutions of the monomers containing chain stabilizers, catalysts and opacifying agents, the polymerization being provided by usual methods.

It should be noted that according to the invention, the manganous silicate may be incorporated at any operation stage, for instance, adding it to the monomer or the partly formed polymer before putting the autoclave under vacuum or to the polymer already formed as chips before their spinning.

In any case there are obtained white polymers giving light fast yarns even though having a high content of opacifying titanium oxide (2 to 3 percent).

EXAMPLE I Into a 20 litre autoclave there are put 10 kg. of caprolactam containing 45 gr. of titanium dioxide of the anatase type, 500 gr. of water, 18 gr. of acetic acid and 10 gr. of natural manganous silicate finely crushed and purified the manganese content of which corresponds to 28% by weight.

Within two hours the autoclave is heated to 250 C. venting it from time to time to eliminate the steam. Under continuous stirring and at atmospheric pressure the autoclave is held at same temperature for further 14 hours, after which time it is put gradually under vacuum to ob tain a residual pressure of 260 mm. Hg within two hours time.

The polymer formed is finally extruded by the pressure of an inert gas, cooled and cut into uniform chips.

The polymer obtained is perfectly white and its visco6sity in sulfuric acid (concentration of 1%) is equalto 2. 5.

After washing and drying, the polymer is spun on a head wit-h a melting grid providing single 15 denier yarns and 6 filament yarns of 30 deniers.

' The stability in the presence of light is measured by the loss of tenacity obtained on purified and fixed strips made with the experimental yarn obtained, after exposure to light in the F ade-Ometer apparatus of the Atlas Electric Devices Company, of Chicago, under the conditions de 3 fined by the ASTM Standards for textile material, designation D 506-50 T (edition 1951, pages 174 ff.).

The improved light fasteness of a yarn obtained from said polymer is readily apparent. In fact, after 100 hours of exposure, in the Fade-Ometer, there is found an average of tenacity loss of 2% for the count 15/1 and 3.5% for the count 30/ 6. On the contrary, the yarn made of a polymer obtained under the conditions described hereinabove, without the addition of manganous silicate, shows, after 100 hours of exposure to light an average tenacity loss of 42% for the count 15/1 and 56% for the count 30/ 6.

Example II The operation is the same as for Example I, however with the use of 200 gr. of titanium dioxide of the anatase type as opacifier (correspondintg to 2% by weight of the monomer).

The polymer obtained is prefectly white and its relative viscosity in sulfuric acid is equal to 2.80.

The average loss of tenacity of the yarns obtained with said polymer after 100 hours exposure in the Fade- Ometer under the conditions described in the Example I, is equal to 3.5% for the count 15/1 and to 5% for the count 40/10 as compared with an average loss of 41% for the count 15/1 and of 69% for the count 40/ observed in a yarn coming from a polymer obtained under similar conditions without any addition of manganous silicate.

Example Ill The operation is the same as in Example I, but with the use of 1.8 gr. of natural crushed manganous silicate containing 28% by weight of Mn. The polymer obtained is perfectly white and its visocity in sulfuric acid is equal to 2.66. The average loss of tenacity of the yarns obtained from said polymer after 100 hours of exposure in the Fade-Ometer under the conditions described in Example I, is equal to 6% for the count /1 and 9% for the count 30/6 as compared with the loss already disclosed in Example I for a yarn containing no manganous silicate.

Example IV The operation is the same as in Example I but with the use of 13 gr. of finely crushed artificial mangaanous containing 28% by weight of Mn as stabilizer.

The polymer obtained is perfectly white and its viscosity in sulfuric acid is 2.70. The average loss of tenacity of the yarns obtained from said polymer after 100 hours of exposure in the Fade-Ometer under the conditions described in Example I, is equal to 1% for the count 15/1 and to 2% for the count 30/6 as compared with the loss already disclosed in Example I for a yarn made without any addition of manganous silicate.

Example V The operation is the same as in Example I, but with the use of 13 gr. of finely crushed artificial manganous silicate, the manganese content of which is equal to 22% by weight as a stabilizer to light degradation.

The data concerning such a polymer and the yarn obtained therewith, are equal to those given for the polymer and the yarn obtained in conformity with Example I.

Example VI Into a litre autoclave there are introduced 8 kg. of adipate of hexamethylenediammonium containing 0.32%

by weight of acetic acid, 0.45% of titanium dioxide of the anatase type, 3.450 kg. of distilled water and 9 gr. of finely crushed manganous silicate containing 22% by weight of metallic manganese.

The autoclave is heated to the temperature of 110 C.

thus removing 50% of the water introduced by distilperature is then raised to 250 C., the pressure however being maintained at 5 atmospheres by venting'the autoclave.

The pressure during 1 hour is gradually lowered to autmospheric pressure, while the mass under continuous stirring is heated to 275 C. and maintained during 2 hours at said temperature and pressure.

Vacuum is then applied thus bringing gradually the autoclave to a pressure of a few mm. of mercury within 1 hour, and maintaining said reduced pressure during further half an hour. Finally, the pressure is restored with a dried inert gas and a polymer obtained is extruded. cooled and cut into uniform chips.

The polymer obtained is perfectly white and is intrinsic viscosity in metacresol is 1.06.

The average loss of tenacity of the yarn obtained from said polymer after hours of exposure to the Fade- Ometer under the conditions described in Example I, is equal to 3% for the count 15/1 and to 5% for the count 30/6, as compared with an average loss of 32% for the count 15/1 and of 48% for the count 30/6 of a yarn made of a polymer obtained under the same conditions but without any incorporation of manganous silicate.

Example VII The operation is the same as in Example I with the use however of a monomer constituted by 13 kg. of warnino-undecanoic acid containing 0.28% by weight of acetic acid, 58.5 gr. (0.45% by weight) of titanium dioxide of the anatase type, 4.250 kg. of distilled water and 12.5 gr. of finely crushed natural manganous silicate containing 0.28% by weight of manganese metal.

The autoclave is heated to C. in about 2 hours showing then a pressure of 8 atmospheres. The temperature is raised still further to 225 C., while maintaining the pressure at its value of 8 atmospheres by venting the autoclave. Then the pressure is gradually lowered within 2 hours to atmospheric pressure while the temperature of the mass is raised to 260 C. Maintaining these conditions the mass is stirred for 4 hours. Then for half an hour into the autoclave there is fed a light stream of an inert gas, and, finally, the polymer obtained is extruded, cooled and cut into uniform chips. The polymer obtained is perfectly white and its viscosity in metacresol is equal to 1.02.

The average loss of tenacity of the yarns obtained from said polymer after 100 hours of exposure in the Fade-Orneter under the conditions described in Example I, is equal to 2% for the count 15/1 and to 3% for the count 30/ 6, as against an average loss of 33% for the count 15/ 1 and of 42% for the count 30/6 measured on a yarn made from a polymer obtained under the same conditions but without any incorporation of manganous silicate.

Example VIII The operation is the same as in Example 1, except for the fact that, instead of being introduced at the beginning of the polymerization, the manganous silicate is added to the polymer already partly formed immediately before the autoclave is vacuated.

The data relating to the polymer and to the yarn obtained therefrom, are the same as those obtained in Example I.

Example IX We claim:

1. A light-stabilized, substantially color-free, substantially light-fast yarn comprising a fiber-forming polyamide and containing from .005 to .05 percent by weight of manganous silicate, calculated as metallic manganese,

evenly incorporated therein and consisting of crushed particles of diameter less than microns.

2. The light-stabilized yarn defined in claim 1, wherein the said polyamide is polycaprolactam.

3. The light-stabilized yarn defined in claim 1, having further included therein titanium dioxide not to exceed three percent by weight.

4. The light-stabilized yarn defined in claim 1, wherein at least 90 percent by weight of said manganous silicate consists of particles of diameter less than 5 microns.

5. A process for producing a substantially color-free, light-stabilized polyamide yarn, comprising the steps of evenly incorporating crushed particles of manganous silicate of a diameter less than ten microns into a polyamide, and of spinning filaments of said silicate-containing polyamide.

6. The process defined in claim 5, wherein the said manganous silicate comprises from to 43 percent by weight of manganese calculated as metallic manganese.

7. The process defined in claim 5, wherein at least 90 percent by weight of the manganous silicate powder consists of particles having a diameter not greater than 5 microns.

References Cited by the Examiner UNITED STATES PATENTS 2,201,741 5/1940 Owens et al. 26078 2,887,462 5/ 1959 Van Oot 260--45.75 3,009,900 11/1961 Hansen 26045. 75 3,019,210 1/1962 Gilles 26045.7 3,066,034 11/ 1962 Temin 260 .75 3,206,430 9/1965 Corbin et al. 260-45.75

FOREIGN PATENTS 737,943 8/ 1943 Germany.

LEON I. B'ERCOVITZ, Primary Examiner.

DONALD E. CZAJA, G. W. RAUCHFU SS, JR.,

Assistant Examiners. 

1. A LIGHT-STABILIZED, SUBSTANTIALLY COLOR-FREE, SUBSTANTIALLY LIGHT-FAST YARN COMPRISING A FIBER-FORMING POLYAMIDE AND CONTAINING FROM .005 TO .05 PERCENT BY WEIGHT OF MANGANOUS SILICATE, CALCULATED AS METALLIC MANGANESE, EVENLY INCORPORATED THEREIN AND CONSISTING OF CRUSHED PARTICLES OF DIAMETER LESS THAN 10 MICRONS. 